Airfoil vacuum pump with tapered rotor

ABSTRACT

An airfoil vacuum pump of the centrifugal type has a rotor disposed in a conical housing. The rotor has vanes that taper radially inwardly away from the rotor toward the axial inlet of the pump. The leading and trailing edges of the vanes converge in a direction toward the inlet, and the thickness of the vanes decreases in that direction.

United States Patent [191 Daniel 1 May 22, 1973 [541 AIRFOIL VACUUM PUMPWITH TAPERED ROTOR [76] Inventor: William H. Daniel, 541

Road, Rogers, Ark. 72756 [22] Filed: June 23, 1971 [21] App1.No.:155,766

Putrnan [52] U.S. Cl ..415/2l3, 416/176 [51] Int. Cl. ..F04d 7/02, F04d29/22 [58] Field of Search ..415/2l3, 212, 72;

[56] References Cited UNITED STATES PATENTS 2,202,790 5 1940 Forrest..41s/213 3,261,297 7/1966 Daniel ..415/213 FOREIGN PATENTS ORAPPLICATIONS 568,031 12/1958 Canada ..415/2l3 Primary Examiner-l-lenryF. Raduazo Attorney-Young & Thompson [57] ABSTRACT An airfoil vacuumpump of the centrifugal type has a rotor disposed in a conical housing.The rotor has vanes that taper radially inwardly away from the rotortoward the axial inlet of the pump. The leading and trailing edges ofthe vanes converge in a direction toward the inlet, and the thickness ofthe vanes decreases in that direction.

10 Claims, 5 Drawing Figures AIRFOIL VACUUM PUMP WITH TAPERED ROTOR Thepresent invention relates to centrifugal pumps, more particularly of theairfoil vacuum type in which a rotor carries a plurality of vanes ofairfoil configuration, the inlet to the pump being generally axiallydisposed and the outlet generally peripherally disposed.

It is an object of the present invention to provide an airfoil pump ofthe centrifugal type, of greatly increased efficiency.

Another object of the present invention is the provision of such a pumpthat is free of cavitation.

Still another object of the present invention is the provision of such apump, in which substantially laminar flow is achieved.

Finally, it is an object of the present invention to provide such apump, which will be relatively simple and inexpensive to manufacture,easy to operate, maintain and repair, and rugged and durable in use.

Briefly, the objects of this invention are achieved by providing anairfoil pump of the centrifugal type, in which a rotor has a pluralityof outwardly extending vanes of generally airfoil configuration,characterized in that the pump casing is tapered toward the axial intakeof the pump, and in that the vanes are radially inwardly inclined in thedirection away from the rotor and toward the inlet. In this way, thewidth of the pump casing is at a maximum on its axis and progressivelydecreases in a radially outward direction, the pitch diameter of thevanes correspondingly increasing in the same direction and thecross-sectional area of the vanes increasing in the same direction, sothat the tangential velocity and the pressure-of the pumped fluidprogressively increase in a direction radially outward from the axis ofthe pump.

These and other objects, features and advantages of the presentinvention will become apparent from consideration of the followingdescription taken in connection with the accompanying drawing, in which:

FIG. 1 is a view along the axis of the pump of the present invention,taken in the inlet direction, partly in cross section on the line 11 ofFIG. 2;

FIG. 2 is a cross-sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a perspective view of one form of the rotor of the pump of thepresent invention;

FIG. 4 is a view similar to FIG. 3 but showing another embodiment of therotor; and

FIG. 5 is a somewhat schematic cross-sectional view of a vane accordingto the present invention.

Referring now to the drawing in greater detail, there is shown a pump ofthe centrifugal type according to the present invention, comprising acasing 1 in two portions 3 and 5. Portion.3 is generally-in the form ofa flat plate, while portion 5 is generally conical and tapers from anaxially disposed inlet 7 at the apex of the cone, radially outwardly toa generally tangentially disposed outlet 9 at the outer periphery of thecone. Casing portions 3 and 5 are secured together peripherally and thusdefine between them a pump chamber 11.

Disposed in chamber 11 coaxially therewith is a rotor 13 comprising ashaft 15 that extends through casing portion 3 and is supported thereinby means of a bearing 17. Means (not shown) are provided to rotate shaft15 to drive the pump. The rotor proper comprises a flat circular plate19 secured to the left end of shaft 15 as seen in FIG. 2 in spacedrelationship to casing portion 3 but parallel thereto.

Plate 19 carries thereon at least one vane 21, on the side plate 19opposite shaft 15. It is possible to provide only one vane 21 if rotor13 is appropriately counterbalanced; but it is preferred to provide aplurality of vanes 21 equally peripherally spaced about rotor 13. FIG. 3shows an embodiment of rotor with four such vanes, while FIG. 4 shows anembodiment of rotor with two such vanes.

Each vane 21 is radially inwardly inclined from its base 23 to its tip25, preferably along generally conical elements that more or lessclosely parallel those of casing portion 5. Each vane 21 also has aleading edge 27 and a trailing edge 29 which converge in a directionaway from the rotor plate 19. The thickness or depth of each vane 21 atits base is also greater than at its tip. The cross-sectional area ofeach vane is accordingly greatest at its base and decreasesprogressively to its tip.

FIG. 5 shows the general cross-sectional configuration of a vane of thepresent invention, which general configuration remains the samethroughout the length of the vane, although, as indicated above, thedimensions of the cross-sectional configuration progressively vary. InFIG. 5, the leading and trailing edges are again seen at 27 and 29, andthe intersections of the cross section with that radius that passesthrough the region of greatest thickness of the blade, locate theelement 31 on the outer side of the vane and the element 33 on the innerside. When speaking of elements it is of course understood each blade ispreferably bounded by an infinite number of straight lines which are theboundary elements of the vane.

With further reference to FIG. 5, it will be noted that the leading edge27 is about half the radial distance between the radially outermost partof the vane and the radially innermost part thereof. Thus, the outerleading surface of the vane, from 27 to 31, subjects the fluid topressure in an axially outward direction, while the leading surface ofthe blade from 27 to 33 imparts an equal and opposite force to anotherportion of the fluid, so that the influences of the two leading portionsof the vane cancel each other.

The portion of the vane from element 31 to the trailing edge 29 ispreferably concentric or substantially concentric with the pump, notvarying more than a few degrees either way from concentricity. However,the portion of the inner surface of the vane from element 33 to trailingedge 29 traverses the entire radial extent of the vane. Thus, while thesurface 31-29 imparts substantially no outward thrust to the fluid,the-surface 33 to 29 extends over the full thickness of the vane andhence exerts maximum radial outward force on the fluid.

In operation, a fluid such as water entering chamber 11 from inlet 7flows into an axially central portion of chamber 11 and initially comesunder the influence of the radially innermost tips 25 of the vanes 21.As these tips are disposed relatively close to the axis of rotation ofrotor 13, their tangential velocity is lower than the tangentialvelocity of any other portion of the vanes. Also, as theircross-sectional area is the smallest part of the vane and all theireffective surfaces are correspondingly reduced in size, the tips 25exert the least influence on the fluid of any portion of the vanes.

In other words, fluid entering chamber 11 at inlet pressure and withsubstantially no speed of rotation, is initially increased in pressureand caused to begin to rotate, by the portion of the vanes 21 whichexerts the most gentle action in these respects, by virtue both of thesmallest area and of the smallest tangential speed of rotation of thetips of the vanes. This gentlest action of the tips of the blades isaugmented by the fact that the fluid at this point is in the widestportion of tapering chamber, that is, nearest the axis of the chamber.

As the fluid begins to circulate in the chamber, it flows radiallyoutwardly in the chamber, and several things simultaneously happen: inthe first place, the fluid encounters a portion of the vanes 21 closerto the base 23 thereof and hence radially farther out than the tips ofthe vanes. The radially farther out portions of the vanes rotate fasterthan the tips of the vanes, so that the fluid progressively contactsportions of the vanes rotating at progressively higher tangentialvelocities. At the same time, the cross-sectional configuration of theportion of the vane contacted by the liquid is increasing in size, fromthe least cross section at the tip 25 to the greatest cross section atthe base 23, so that the pressure, or rather the suction, exerted by thevane on the fluid is increasing because the size of the vane isincreasing. Also at the same time, as the fluid moves radially outwardin the chamber 11, the chamber 11 is becoming progressively narrower, sothat the liquid must travel with higher and higher tangential velocity.

All these factors coact to achieve a smooth laminar flow in the pump ofthe present invention, with greatest efficiency and with leastcavitation even when the inlet is substantially closed. These improvedresults depend not on precision of manufacture and close tolerances, butrather on the factors recited above, so that the pump can be constructedwithout great attention to precision of manufacture, in other words,inexpensively.

In consideration of the foregoing disclosure, therefore, it will beevident that all of the initially recited objects of the presentinvention have been achieved.

Although the present invention has been described and illustrated inconnection with preferred embodi' merits, it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit of the invention, as those skilled in this art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the present invention as defined by theappended claims.

Having described my invention, 1 claim:

1. An airfoil pump comprising a casing having an axially disposed inletand a peripherally disposed outlet and tapering from a greatest axialwidth adjacent the inlet to a least axial width adjacent the outlet, anda rotor rotatably disposed in the casing, said rotor bearing at leastone airfoil vane that extends away from the rotor and is inclinedradially relative to the axis of rotation of the rotor, said at leastone vane having leading and trailing edges that converge in a radiallyinward direction.

2. A pump as claimed in claim 1, said casing being conical.

3. A pump as claimed in claim 1, said edges converging in a directionaway from the rotor.

4. A pump as claimed in claim 1, said at least one vane having anairfoil cross-sectional configuration whose length and widthprogressively decrease in the direction away from the rotor.

5. A pump as claimed in claim 1, said rotor comprising a flat plate onwhich said at least one vane is mounted, said plate being spaced frombut closely adjacent a flat plate comprising one side of said casing,said rotor having an axial drive shaft extending through the last-namedflat plate.

6. A pump as claimed in claim 1, the radially outer surface of said atleast one vane, from the region of greatest thickness of the vane to thetrailing edge of the vane, being substantially concentric with saidrotor.

7. A pump as claimed in claim 1, said vane having an airfoilcross-sectional configuration characterized by a leading edge and atrailing edge and a region of greatest thickness between said leadingand trailing edges, the radially outer surface of said vane between saidregion of said greatest thickness and said trailing edge beingsubstantially concentric with said rotor.

8. A pump as claimed in claim 1, said inlet and said rotor beingdisposed on opposite axial sides of said casmg.

9. A pump as claimed in claim 8, said casing being conical.

10. A pump as claimed in claim 9, said casing having radially outer sidewalls that are inclined in substantially the same direction as said atleast one vane.

1. An airfoil pump comprising a casing having an axially disposed inletand a peripherally disposed outlet and tapering from a greatest axialwidth adjacent the inlet to a least axial width adjacent the outlet, anda rotor rotatably disposed in the casing, said rotor bearing at leastone airfoil vane that extends away from the rotor and is inclinedradially relative to the axis of rotation of the rotor, said at leastone vane having leading and trailing edges that converge in a radiallyinward direction.
 2. A pump as claimed in claim 1, said casing beingconical.
 3. A pump as claimed in claim 1, said edges converging in adirection away from the rotor.
 4. A pump as claimed in claim 1, said atleast one vane having an airfoil cross-sectional configuration whoselength and width progressively decrease in the direction away from therotor.
 5. A pump as claimed in claim 1, said rotor comprising a flatplate on which said at least one vane is mounted, said plate beingspaced from but closely adjacent a flat plate comprising one side ofsaid casing, said rotor having an axial drive shaft extending throughthe last-named flat plate.
 6. A pump as claimed in claim 1, the radiallyouter surface of said at least one vane, from the region of greatestthickness of the vane to the trailing edge of the vane, beingsubstantially concentric with said rotor.
 7. A pump as claimed in claim1, said vane having an airfoil cross-sectional configurationcharacterized by a leading edge and a trailing edge and a region ofgreatest thickness between said leading and trailing edges, the radiallyouter surface of said vane between said region of said greatestthickness and said trailing edge being substantially concentric withsaid rotor.
 8. A pump as claimed in claim 1, said inlet and said rotorbeing disposed on opposite axial sides of said casing.
 9. A pump asclaimed in claim 8, said casing being conical.
 10. A pump as claimed inclaim 9, said casing having radially outer side walls that are inclinedin substantially the same direction as said at least one vane.